Copolymerizable phoinitiators for uv-crosslinkable adhesives

ABSTRACT

The invention relates to radically copolymerizable acetophenone or benzophenone derivatives, which may be obtained by reacting a) acrylic or methacrylic compounds, which contain at least one isocyanate-reactive group [compounds a)], with b) compounds, which contain at least two isocyanate groups [compounds b)] and c) acetophenone or benzophenone derivatives, which contain at least one isocyanate-reactive group [compounds c)]. Said invention also relates to copolymers, which contain said copolymerizable photoinitiators, as well as to the use of said copolymers in V-crosslinkable substances, in particular hot-melt pressure-sensitive adhesives.

[0001] The invention relates to radically copolymerizable acetophenoneor benzophenone derivatives (referred to below as “copolymerizablephotoinitiators” for the sake of brevity), obtained by the reaction of

[0002] a) (meth)acrylic compounds, having at least oneisocyanate-reactive group [compounds a)] with

[0003] b) compounds having at least two isocyanate groups [compounds b)]and

[0004] c) acetophenone or benzophenone derivatives having at least oneisocyanate-reactive group [compounds c)].

[0005] The invention also relates to copolymers which contain thecopolymerizable photoinitiators of the invention and to the use of thecopolymers in UV-crosslinkable compositions, for example, as adhesives,particularly hot-melt adhesives.

[0006] UV-crosslinkable adhesives containing photoinitiators in the formof polymerized units, are disclosed, for example, in specifications DE-A2,411,169 and EP-A 246,848.

[0007] Copolymerizable benzophenone or acetophenone derivatives aredescribed, for example, in specifications EP-A 346,788 and EP-A 377,199.

[0008] Copolymerizable photoinitiators should be producible in a simplemanner and be readily copolymerizable, and the copolymers containingphotoinitiators should exhibit, in use, good application-technologicalproperties, particularly high cohesion and adhesion when used asadhesives.

[0009] It is an object of the present invention to provide novelcopolymerizable photoinitiators, and copolymers containing thephotoinitiators of the invention in the form of polymerized units andexhibiting, when used as adhesives, improved cohesion and adhesion.

[0010] Accordingly, we have found the copolymerizable photoinitiatorsdefined above, copolymers containing the same, and the use thereof inUV-crosslinkable compositions.

[0011] The compounds a) are, for example, (meth)acrylic compounds of thegeneral formula (I)

H₂C═CR¹—C(═O)—X—R²(—Y)_(π)  (I),

[0012] in which the substituents and indices have the followingmeanings:

[0013] R¹ denotes —H, —CH₃,

[0014] X denotes —O—, —NH—, —NR³— or —S—, preferably —O—,

[0015] R³ denotes linear or branched C₁-C₆ alkyl,

[0016] R² denotes a (π+1)-binding,

[0017] optionally substituted linear or branched Cl-C₁₋₂ alkyl group,preferably a C₂-C₈ alkyl group, or

[0018] a C₃-C₁₂ cycloalkyl group, optionally substituted, preferably

[0019] a C5 and C₆ cycloalkyl group, or

[0020] a C₆-C₁₀ aryl group, optionally substituted, preferably a phenylgroup,

[0021] Y denotes —OH, —NH2, —NHR³ or —SH, preferably —OH,

[0022] π is a number from 1 to 5, preferably 1.

[0023] In formula (I) the structural element —R²(—Y)_(π) canalternatively be a group of the general formula (II), (III) or (IV)

—(EO)_(k)—(PO)_(l)—H  (II),

—(PO)_(l)—(EO)_(k)—H  (II),

—(Eo_(k)/PO_(l))—H  (IV), in which

[0024] EO stands for a —CH₂—CH₂—O group,

[0025] PO stands for a —CH₂—CH(CH₃)-0 or a —CH(CH₃)—CH₂—O group and kand l for numerical values from 0 to 15, frequently from 0 to 10 andoften from 0 to 5, but k and l are not both 0. Frequently either k or lis equal to 1, 2, 3, or 4 and often to 1.

[0026] Furthermore, in formulas (II) and (III)

[0027] (EO)_(k) should denote a block of k —CH₂—CH₂—O groups, and(PO)_(l) a block of l —CH₂—CH(CH₃)—O or —CH(CH₃)—CH₂—O groups, and

[0028] in formula (IV) (EO_(k)/PO_(l)) should denote a mixture of k—CH₂—CH₂—O groups and l —CH₂—CH(CH₃)—O or —CH(CH₃)—CH₂—O groups inrandom distribution.

[0029] A significant fact is that in formulas (II), (III), or (IV)either EO or PO can be replaced by BO, where BO stands for a—CH₂—CH(C₂H₅)—O or a —CH(C₂H₅)—CH₂—O group as well as a —CH₂—C(CH₃)₂-°or a —C(CH₃)₂—CH₂-0 group.

[0030] By linear or branched C₁-C₆ alkyl is meant linear or branchedalkyl containing from 1 to 6 carbons, for example, methyl, ethyl,n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, npentyl,isopentyl, tert-pentyl, n-hexyl, isohexyl, or tert-hexyl.

[0031] By a (π+1)-binding, linear or branched C₁-C₁₂ alkyl group we meanalkyl derived from, for example, methyl, ethyl, propyl, 2-methylpropyl,2,2-dimethylpropyl, and n-butyl and isomers thereof, npentyl and isomersthereof, n-hexyl and isomers thereof, n-heptyl and isomers thereof,n-octyl and isomers thereof, n-nonyl and isomers thereof, n-decyl andisomers thereof, n-undecyl and isomers thereof, or n-dodecyl and isomersthereof. Of course, the aforementioned alkyl groups may be substitutedby further mono-, di-, or tri-functional groups, such as halogens, iefluorine, chlorine, or bromine, or alkoxyl groups, such as methoxy,ethoxy, or butoxy groups, in which case the covalence of the alkylgroups rises by the number of such substituents.

[0032] By (π+1)-binding C₃-C₁₂ cycloalkyl groups we mean (π+1)-bindingcycloalkyl groups derived, for example, from cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, orcyclodecyl. Furthermore they may be taken to mean bicyclic compoundsderived from bicyclohexane, bicycloheptane, bicyclooctane,bicyclononane, bicyclodecane, and bicycloundecane or bicyclododecane. Ofcourse, the aforementioned cycloalkyl groups may be substituted byfurther mono-, di-, or tri-functional groups, such as C₁-C₆ alkylgroups, halogens, or alkoxyl groups, in which case the covalence of thecycloalkyl rises by the number of such substituents. Frequently1,2-cyclopropylene, [1,2 or 1,3]-cyclobutylene, [1, 2 or1,3]-cyclopentylene, [1,2, 1,3, or 1,4]-cyclohexylene, [1,2, 1,3, or1,4]-cycloheptylene, bicyclooctylene, bicyclononylene, bicyclodecyleneand bicycloundecylene groups are used.

[0033] By (π+1)-binding C₆-C₁₀ aryl groups we mean (π+1)-binding arylgroups derived from phenyl or naphthyl groups. Of course, theaforementioned aryl groups may be substituted by 1, 2, or 3substituents, such as C₁-C₆ alkyl groups, halogens, or alkoxyl groups,in which case the covalence of the aryl groups rises by the number ofthese substituents. Frequently, use is made, in particular, of [1,3 and1,4]-phenylene or [1,3, 1,4, 1,5, and 2,6]-naphthylene groups.

[0034] An essential feature is that the aforementioned groups R² aresubstituted by π Y groups. π denotes here a number from 1 to 5, forexample, 1, 2, 3, 4 or 5, but particularly 1.

[0035] Compounds a) used are, in particular: 2-hydroxyethyl(meth)acrylate, 2-hydroxy-2-methylethyl (meth)acrylate, 3-hydroxypropyl(meth)acrylate, 2-hydroxy-2-ethylethyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate, further neopentyl glycol mono(meth)acrylate, glycerolmono(meth)acrylate, trimethylolpropane mono(meth)acrylate,pentaerythritol mono(meth)acrylate, N-hydroxymethyl(meth)acrylamide, andN-hydroxyethyl(meth)acrylamide, 5-hydroxy-3-oxopentyl(meth)acrylamide,N-hydroxymethylcrotonamide or N-hydroxyethylmaleinimide. Particularpreference is given to 2-hydroxyethyl (meth)acrylate, 3-hydroxypropylacrylate, and 4-hydroxybutyl (meth)acrylate.

[0036] Compounds b) containing at least 2 isocyanate groups usuallyexhibit the structure of the general formula (V)

Q(—NCO)_(λ)  (V).

[0037] In formula (V), Q should denote, for example,

[0038] a linear or branched C₃-C₁₆ alkane compound, for example,propane, 2-methylpropane, 2,2-dimethylpropane, n-butane and isomersthereof, n-pentane and isomers thereof, n-hexane and isomers thereof,n-heptane and isomers thereof, n-octane and isomers thereof, n-nonaneand isomers thereof, n-decane and isomers thereof, n-undecane andisomers thereof, and n-dodecane and isomers thereof, n-tridecane andisomers thereof, n-tetradecane and isomers thereof, n-pentadecane andisomers thereof and also n-hexadecane and isomers thereof, preferably aC₆-C₁₃ alkane compound, optionally substituted by 1, 2 or 3 halogens,oxo, ester, or alkoxy groups, or

[0039] a C₆-C₁₄ aromatic compound, for example, benzene,diphenylmethane, naphthalene, phenanthrene, preferably benzene anddiphenylmethane, optionally substituted by 1, 2, or 3 halogens, C₁-C₆alkyl, oxo, ester, or alkoxy groups, or

[0040] a C₃-C₁₆ cycloalkane compound, for example, cyclopropane,cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane,bicyclooctane, bicyclononane, bicyclodecane, bicycloundecane,bicyclododecane, and bis(cyclohexyl)methane, preferably cyclopentane,cyclohexane, bis(cyclohexyl)methane, optionally substituted by 1, 2, or3 halogens, C₁-C₆ alkyl, oxo, ester, or alkoxy groups, or

[0041] an arylalkyl compound containing from 6 to 10 carbons in the arylmoiety and from 1 to 6, preferably from 1 to 4 carbon atoms in the alkylmoiety, optionally further substituted by 1, 2, or 3 halogens, oxo,ester, or alkoxy groups,

[0042] which is substituted by λ isocyanate groups (—NCO), λ, whichdenotes the average functionality, being a number ≧2, often a numberfrom 2 to 6, and frequently a number from 2 to 4. In particular, λ isequal to 2.

[0043] Examples of compounds of the general structure (V) are aliphatic,cycloaliphatic, and aromatic isocyanates known from the prior art.Preferred di- or poly-isocyanates are 4,4′-diphenylmethane diisocyanate,the mixtures of monomeric diphenylmethane diisocyanates and oligomericdiphenylmethane diisocyanates (polymeric MDI), tetramethylenediisocyanate, tetramethylene diisocyanate trimers, hexamethylenediisocyanate, hexamethylene diisocyanate trimers, isophoronediisocyanate trimer, 4,4′-methylenebis(cyclohexyl) diisocyanate,xylylene diisocyanate, tetramethylxylylene diisocyanate, [1,3 and1,4]-bis(isocyanatomethyl)cyclohexanes, dodecyl diisocyanate, lysinealkylester diisocyanate, alkyl standing for C₁ to C₁₀, [2,2, 4 or2,4,4]-trimethyl-1,6-hexamethylene diisocyanate,1,4-diisocyanatocyclohexane or 4-isocyanatomethyl-1,8-octamethylenediisocyanate.

[0044] Special preference is given to di- or poly-isocyanates containingisocyanate groups of different reactivity, such as 2,4-toluylenediisocyanate (2,4-TDI), 2,4′-diphenylmethane diisocyanate (2,4′-MDI),triisocyanatotoluene, isophorone diisocyanate (IPDI),2-butyl-2-ethylpentamethylene diisocyanate, and2-isocyanatopropylcyclohexyl isocyanate,3(4)isocyanatomethyl-1-methylcyclohexyl isocyanate,1,4-diisocyanato-4-methylpentane, 2,4′-methylenebis(cyclohexyl)diisocyanate and 4-methylcyclohexane 1,3-diisocyanate (H-TDI).

[0045] Furthermore, those isocyanates are particularly preferred whoseisocyanate groups are originally equally reactive, but in which initialaddition of an alcohol, thiol, or amine to one of the isocyanate groupscan induce a reduction of the reactivity of the second isocyanate group.Examples thereof are isocyanates whose isocyanate groups are coupledthrough a delocalized electron system, eg, [1,3 and 1,4]-phenylenediisocyanate, 1,5-naphthylene diisocyanate, diphenyl diisocyanate,tolidine diisocyanate, or 2,6-toluylene diisocyanate.

[0046] Another significant fact is that suitable compounds of thegeneral formula (V) are also those di- and poly-isocyanate compoundswhich can be produced from said di- or poly-isocyanates or mixturesthereof by linking through urethane, allophanate, urea, biuret,uretdione, amide, isocyanurate, carbodiimide, uretoneimine,oxadiazinetrione, or iminooxadiazinedione structures.

[0047] Compounds c) used in the present invention exhibit, for example,a structure conforming to general formula (VI)

A-C(═O)-B-D  (VI),

[0048] in which

[0049] A denotes C₁-C₃ alkyl, such as methyl, ethyl, n-propyl, orisopropyl, C₆-C₁₀ aryl, optionally substituted by 1, 2 or 3 halogens,C₁-C₆ alkyl, esters or alkoxy groups, for example, phenyl or naphthyl,and aralkyl containing from 6 to 10 carbons in the aryl moiety and from1 to 6 carbon atoms in the alkyl moiety, for example, benzyl,

[0050] B denotes C₆-C₁₀ arylene, such as 1,2-, 1,3- and 1,4-phenylene,1,2-, 1,3-, 1,4-, 1,5- and 2,6-naphthylene, optionally substituted by 1,2, or 3 halogens, C₁-C₆ alkyls, esters, or alkoxy groups and

[0051] D denotes —NH2, —NHR³, OH, SH, or a structural element—X—R²(—Y)_(π), the variants having the meanings stated above for formula(I).

[0052] The acetophenone or benzophenone derivatives conforming to thegeneral formula (VI) can, for example, be [2, 3, or4]-hydroxyacetophenone, [2, 3 or 4]-hydroxypropiophenone, [2, 3, or4]-(2-hydroxyethoxy)acetophenone, [2, 3, or 4]-aminoacetophenone, [2-, 3or 4]-aminopropiophenone, and [2, 3, or 4]-hydroxybenzophenone,2-hydroxy-5-methylbenzophenone, 5-chloro-2-hydroxybenzophenone,2-hydroxy-4-methylbenzophenone, [2, 3, or4]-(2-hydroxyethoxy)benzophenone, 4-hydroxy-4′-methoxybenzophenone, and[2, 3, or 4]-aminobenzophenone, [2, 3, or 4]-anilinobenzophenone,2-amino-4-methylbenzophenone, 2-amino-4′-methylbenzophenone,2-amino-4′-chlorobenzophenone, or 2-amino-5-chlorobenzophenone.

[0053] In particular, preference is given to [2 or4]-hydroxyacetophenone, [2 or 4]-hydroxypropiophenone, [2 or4]-(2-hydroxyethoxy)acetophenone, [2 or 4]-aminoacetophenone, [2 or4]-aminopropiophenone, and [2 or 4]-hydroxybenzophenone, [2 or4]-(2-hydroxyethoxy)benzophenone, and [2 or 4]-aminobenzophenone used.

[0054] The copolymerizable photoinitiators are usually produced byplacing at least one compound b), frequently together with an organicsolvent, in a reaction vessel under an atmosphere of inert gas,preferably nitrogen, where it is heated to the reaction temperature withstirring. There is then added, continuously or batchwise, at least onecompound a) at the reaction temperature. The amount of compound a) isgoverned by the number n of isocyanatereactive groups and is usuallysuch-that the ratio of the number of mols of compound b) to the productof the number of moles of compound a) and the number π is from 0.8 to 1to 1 to 0.8 or from 0.9 to 1 to 1 to 0.9 or from 0.95 to 1 to 1 to 0.95.If compound a) has, for example, only one isocyanate-reactive group Y(π=1), there are used, per mol of compound b), ≧0.8 mol, ≧0.9 mol, or≧0.95 mol and ≦1.05 mol, ≦1.11 mol, or ≦1.25 mol of compound a). Ifhowever, compound a) possesses, for example, two isocyanate-reactivegroups Y (π=2), there will be used, per mol of compound b), 20.4 mol,≧0.45 mol, or ≧0.48 mol and ≦0.53 mol, ≦0.56 mol, or ≦0.63 mol ofcompound a).

[0055] The reaction time is usually such that compound a) reactsquantitatively with compound b). Usually therefore the content ofisocyanate groups in the reaction mixture is monitored during thereaction of compound a) with compound b), which content remains constantwhen compound a) has reacted. Determination of the content of isocyanategroups is familiar to the person skilled in the art and is usuallycarried out by addiing an excess of amine, based on the isocyanategroups, and back titrating the amino groups not consumed with dilutehydrochloric acid as specified in DIN 53,185.

[0056] The aforementioned reaction is particularly successful whencarried out in the presence of a catalyst, which is used in aconcentration of from 0.0001 to 1 wt % and preferably from 0.001 to 0.1wt %, based on the weight of isocyanate compound b). Suitable catalystsare organometallic compounds, specifically organotin, organozinc,organobismuth, or organozirconium compounds. Particularly preferred isdibutyltin dilaurate. Strong bases, preferably nitrogen-containingcompounds, such as tributylamine, quinnuclidine, diazabicyclooctane,diazabicyclononane, or diazabicycloundecane may also be used.

[0057] Suitable solvents are anhydrous organic solvents, such asacetone, 2-butanone, ethyl acetate, butyl acetate, tetrahydrofuran,dioxan, benzene, toluene, xylene, ethylbenzene, chlorobenzene,dichlorobenzene, dimethylformamide, dimethyl acetamide, orN-methylpyrrolidone. In particular, acetone, 2-butanone,tetrahydrofuran, ethyl acetate, or chlorobenzene are used.

[0058] The reaction temperature is usually from 0° to 120° C.,preferably from 20° to 100° C., and more preferably from 25° to 90° C.The reaction may be carried out under ambient pressure or undersuperatmospheric pressure, for example, under a pressure of ≧0.1 bar,≧0.5 bar, ≧2 bar, or ≧5 bar. Of course, the reaction may be carried outunder subatmospheric pressure, depending on the boiling point of thesolvent, if used.

[0059] In a subsequent second reaction stage, the reaction mixtureemerging from the aforementioned reaction of compounds a) and b) isadmixed with compound c) continuously or batchwise at the reactiontemperature. The amount of compound c) used is governed by its number ofisocyanate-reactive groups and the number of isocyanate groups stillfree in compound b). It is usually such that the isocyanate groups incompound b) are converted quantitatively and can no longer be detectedtitrimetrically as specified in DIN 53,185. This is usually the casewhen the isocyanate content of the reaction mixture is ≦0.1 wt % ofisocyanate groups, which corresponds to the detection limit oftitration.

[0060] Another possibility, of course, is to cause compound b) to reactfirst of all with compound c) and then with compound a) or to causecompound b) to react concurrently with compound a) and compound c).However, it is important that the reactions are controlled such thatafter the addition of compounds a) and c) to the reaction mixture nomore isocyanate can be detected. Preferably however, compound b) iscaused to react first with compound a) and then with compound c).

[0061] The resulting reaction mixtures contain, as products,copolymerizable photoinitiators of the general formula (VII)

[H₂C═CR¹—C(═O)X—R²(—Y′—C(═O)—NH_(π)]_(φ)-Q-[NH—C(═O)-D′-B-C(═O)-A]_((λ-ψ))  (VII),

[0062] in which R¹, X, and R², π, Q, λ, B and A have the meanings givenfor formulas (I), (V) and (VI) and

[0063] φ stands for a number W≧0.8, ≧0.9 or ≧0.95 and ≦1.05, ≦1.11 or≦1.25 in each case divided by the value of π,

[0064] Y′ stands for a group Y in the deprotonated form (—O—, —NH—,—NR³—, —S—) and

[0065] D′ stands for a group D in the deprotonated form [—O—, —NH—,—NR³—, —S— and —XR²(—Y′)π].

[0066] In particular, each of π, ψ and φ denotes a numerical value of 1.

[0067] Preferably the copolymerizable photoinitiators used are compoundsconforming to formula (VII), in which

[0068] R¹ denotes —H, X and Y′ denote —O—, R² denotes ethylene, Qdenotes 2,4-toluenyl, D′ denotes —O—CH₂CH₂—O—, B denotes 1,4-phenyleneand A denotes phenyl, π and W denote ψ and λ denotes 2, or

[0069] R¹ denotes —H, X and Y′ denote —O—, R² denotes ethylene, Qdenotes 3-methylene-3,5,5-trimethyl-1-cyclohexyl, D′ denotes—O—CH₂CH₂—O—, B denotes 1,4-phenylene and A denotes phenyl, π and ψdenote 1 and λ denotes 2, or

[0070] R¹ denotes —H, X and Y′ denote —O—, R² denotes ethylene, Qdenotes 1,6-hexamethylene, D′ denotes —O—CH₂CH₂—O—, B denotes1,4-phenylene and A denotes phenyl, π and ψ denote 1 and λ denotes 2.

[0071] Usually the copolymerizable photoinitiators of the invention areused for copolymerization in the reaction mixture without furtherpurification or removal of solvent.

[0072] The copolymers of the invention are obtained by polymerization ofa mixture of ethylenically unsaturated monomers, in which thephotoinitiators of the invention are usually present in a total amountof from 0.01 to 10 wt %, preferably from 0.05 to 5 wt % and morepreferably from 0.1 to 2 wt %, based, in each case, on the total amountof monomers. Correspondingly, the photoinitiators of the invention areincorporated as polymerized units in the copolymers in concentrations offrom 0.01 to 10 wt %, preferably from 0.05 to 5 wt %, and morepreferably from 0.1 to 2 wt %. It should be noted here that the saidpercentage contents of the polymerized units of ethylenicallyunsaturated copolymerizable photoinitiators incorporated in thecopolymer plus the contents of the other monomers should generallycorrespond to the concentrations of these components in the monomermixture to be polymerized and vice versa.

[0073] The copolymers contain, besides the aforementionedphotoinitiators, polymerized units of the main monomers generally inmajor amounts, comprising in most cases from 50 to 99,99 wt % andpreferably from 70 to 97,5 wt % of esters of preferably C₃₋₆α,β-monoethylenically unsaturated mono- and di-carboxylic acids, suchas, in particular, acrylic acid, methacrylic acid, maleic acid, fumaricacid, and itaconic acid, with generally C₁₋₁₂, preferably C₁₋₈ and morepreferably C₁₋₄ alkanols, such as, in particular, methyl, ethyl,n-butyl, isobutyl, and 2-ethylhexyl (meth)acrylates, dimethyl maleate ordi-n-butyl maleate. Suitable comonomers are, in particular, monomersthat are capable of undergoing simple free-radical polymerization, suchas ethylene, vinylaromatic monomers, such as styrene, α-methylstyrene,o-chlorostyrene or vinyl toluenes, esters of vinyl alcohol and C₁₋₁₈monocarboxylic acids, such as vinyl acetate, vinyl propionate,vinyl-n-butyrate, vinyl laurate and vinyl stearate, nitriles ofα,β-monoethylenically unsaturated carboxylic acids, such asacrylonitrile, and C₄-C₈ conjugated dienes, such as 1,3-butadiene andisoprene.

[0074] It is particularly advantageous when the copolymers contain, inaddition to the aforementioned monomers, from 0.1 to 15 wt %, andpreferably from 0.5 to 8 wt % of C₃₋₆ α,β-monoethylenically unsaturatedmono- and di-carboxylic acids, amides thereof, and/or anhydridesthereof, such as, in particular, acrylic acid, methacrylic acid, maleicacid, fumaric acid, itaconic acid, acrylamide, methacrylamide, maleicanhydride, also vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonicacid, styrenesulfonic acid and their water-soluble salts, andN-vinylpyrrolidone.

[0075] The copolymers can contain, in addition to the above monomers,further comonomers incorporated as polymerized units, for example, thosewhich usually increase the structural strength of films produced fromthe copolymers. These ethylenically unsaturated monomers normallyexhibit at least one epoxy, hydroxyl, N-methylol or carbonyl group, orat least two non-conjugated ethylenically unsaturated double bonds.Examples thereof are N-alkylolamides of α,β-monoethylenicallyunsaturated carboxylic acids having from 3 to 10 carbon atoms, of whichN-methylol acrylamide and N-methylol methacrylamide are very muchpreferred, and also their esters with alkanols containing from 1 to 4carbons. Also suitabe are monomers having two alkenyl radicals, monomershaving two vinylidene groups and monomers having two vinyl groups.Particularly advantageous here are the diesters of dihydroxylic alcoholswith α,β-monoethylenically unsaturated monocarboxylic acids, of whichacrylic acid and methacrylic acid are particularly preferred. Examplesof such monomers containing two non-conjugated ethylenically unsaturateddouble bonds are alkylene glycol diacrylates and dimethacrylates such asethylene glycol diacrylate, 1,2-propylene glycol diacrylate,1,3-propylene glycol diacrylate, 1,3-butylene glycol diacrylate,1,4-butylene glycol diacrylates and ethylene glycol dimethacrylate,1,2-propylene glycol dimethacrylate, 1,3-propylene glycoldimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycoldimethacrylates, and divinyl benzene, vinyl methacrylate, vinylacrylate, allyl methacrylate, allyl acrylate, diallyl maleate, diallylfumarate, methylene bisacrylamide, cyclopentadienyl acrylate, triallylcyanurate, or triallylisocyanurate. Particularly significant in thiscontext are in addition C₁-C₈-hydroxyalkyl (meth)acrylates such asn-hydroxyethyl, n-hydroxypropyl or n-hydroxybutyl (meth)acrylates, andcompounds such as diacetoneacrylamide and acetylacetoxyethyl(meth)acrylate. In the present invention, the aforementioned monomersare frequently incorporated as polymerized units in amounts of from 0.1to 10 wt %, based on the total weight of the monomers to be polymerized.

[0076] The manner in which the monomeric components are to be added tothe polymerization vessel during the free-radical polymerization, isknown to the person possessing average skill in the art. These can beplaced in the polymerization vessel as a single initial batch, or theycan be added continuously or batchwise at the rate at which they areconsumed during the free-radical polymerization. Specifically, thisdepends on the chemical nature of the initiator system and on thepolymerization temperature. Preferably a small portion of the monomericcomponents is used as initial batch and the rest is fed to thepolymerization zone at the rate at which it is consumed. Anotherpossibility, of course, is to modify the composition of the monomermixture to be polymerized, during polymerization. These process variantsare known to the person skilled in the art. For example, in theso-called step method first of all a monomer mixture 1 and then amonomer mixture 2 having a different monomeric composition will be fedto the polymerization vessel at the rate at which the monomers areconsumed, whilst in the so-called gradient method the composition of themonomer mixture that is fed to the polymerization vessel will becontinuously changed. Frequently the polymerization is carried out underan atmosphere-of inert gas, for example, under a blanket of nitrogen orargon.

[0077] The copolymers of the invention usually have K values of from 10to 150 and often of from 15 to 100. Determination of the K value iscarried out, usually at 25° C. according to DIN ISO 1628-1, on a 1 wt %strength solution of the copolymer in tetrahydrofuran. Preferably the Kvalue is from 25 to 55 when the copolymer is to be used as a hot-meltadhesive. When the copolymer is to be used in a UV-curable compositionfor coating mineral surfaces, its K value is preferably from 60 to 100.Copolymers designed for use in coating compositions preferably have Kvalues of from 15 to 85.

[0078] The copolymers of the invention can exhibit glass transitiontemperatures of from −70 to +150° C. Depending on the end use,copolymers are frequently required whose glass transition temperaturesare within certain limits. By suitably selecting the ethylenicallyunsaturated monomers to be polymerized, the person skilled in the artcan produce copolymers whose glass transition temperatures aredefinitely in the desired range. If, for example, the copolymers of theinvention are to be used as contactbonding adhesives, the composition ofthe monomer mixture to be polymerized is such that the copolymersproduced have glass transition temperatures of <0° C., frequently ≦+5°C., and often ≦+10° C. If, however, the copolymers are to be used asUV-curable binding agents in coating compositions, the composition ofthe monomer mixture to be polymerized is such that the copolymersproduced show glass transition temperatures of from −40° to +150° C.,frequently from 0° to +100° C., and often from +20° to +80° C.

[0079] By the glass transition temperature T_(g), we mean the limitingvalue of the glass transition temperature which it approaches withincreasing molecular weight as desacribed by G. Kanig(Kolloidzeitschrift & Zeitschrift fr Polymere, Vol. 190, page 1,equation 1). The glass transition temperature is determined by the DSCmethod (Differential Scanning Calorimetry, 20 K/min, mid-point reading,DIN 53,765).

[0080] According to Fox (T. G. Fox, Bull. Am. Phys. Soc. 1956 [Ser. II]1, page 123 and according to Ullmanns Encyclopaedie der technischenChemie, Vol. 19, page 18, 4th Edition, Verlag Chemie, Weinheim, 1980)the following applies to the glass transition temperature of not morethan weakly crosslinked copolymers, as a good approximation:

l/T _(g) =x ¹ /T _(g) ¹ +x ² /T _(g) ² + . . . x ^(n) /T _(g) ^(n),

[0081] in which x¹, x² . . . x^(n) denote the mass fractions of themonomers 1, 2 . . . n and T_(g) ¹, T_(g) ² . . . T_(g) ^(n) denote theglass transition temperatures of the polymers composed of, in each case,only one of the monomers 1, 2 . . . n, in degrees Kelvin. The T_(g)values for the homopolymers of most monomers are known and are listed,for example, in Ullmann's Encyclopedia of Industrial Chemistry, Vol. 5,Vol. A21, page 169, VCH Weinheim, 1992; further sources of glasstransition temperatures of homopolymers are, eg, J. Brandrup, E. H.Immergut, Polymer Handbook, 1^(st) Ed., J. Wiley, New York 1966, 2nd Ed.J. Wiley, New York 1975, and 3rd Ed. J. Wiley, New York 1989).

[0082] The novel copolymers can be produced by copolymerization of themonomeric components using conventional polymerization initiators and,optionally, modifiers, polymerization being carried out at the usualtemperatures in substance, in emulsion, for example, in water orsuitable organic media, or in solution. Preferably, the novel copolymersare produced by polymerization of the monomeric components in organicsolvents, particularly in solvents having a boiling range of from 50° to150° C., preferably from 60° to 120° C., using conventional amounts ofpolymerization initiators, which are generally from 0.01 to 10 wt %, andparticularly from 0.1 to 4 wt %, based, in each case, on the totalweight of the monomeric components. Suitable organic solvents are, inparticular, alcohols, such as methanol, ethanol, n-propanol,isopropanol, n-butanol and isobutanol, cyclic ethers, such astetrahydrofuran, and hydrocarbons, such as toluene and gasolenes boilingat temperatures ranging from 60° to 120° C. Furthermore ketones, such asacetone, methyl ethyl ketone and esters, such as ethyl acetate, andmixtures of solvents of said types can be used, in which case mixturescontaining isobutanol and/or methyl ethyl ketone in amounts of ≧70 wt %,particularly ≧80 wt %, and more particularly ≧90 wt %, based on thesolvent mixture used. are preferred.

[0083] The manner in which the solvent or solvent mixture is added tothe polymerization vessel during the free-radical polymerization, isknown to the person possessing average skill in the art. It can beplaced as a single initial batch in the polymerization vessel, or it canbe used continuously or stepwise during the free-radical polymerization.In addition, the solvent can be used in admixture with the monomersand/or the initiator. Preferably, a major portion of the solvent is usedas initial batch and the rest is fed to the polymerization zone togetherwith the monomers to be polymerized and/or initiators.

[0084] Suitable polymerization initiators for solvent polymerization re,for example, azo compounds, such as 2,2′-azobisisobutyronitrile,2,2′-azobis-2-methylbutyronitrile, diacyl peroxides, such dibenzoylperoxide, dilauroyl peroxide, didecanoyl peroxide, nd diisononanoylperoxide, alkyl peresters, such as tert-butyl perpivalate, tert-butylper-2-ethylhexanoate, tert-butyl permaleate, tert-butyl perisononanoate,and tert-butyl perbenzoate, dialkylperoxides, such as dicumyl peroxideor di-tert-butyl peroxide, peroxydicarbonates, such as dimyristylperoxydicarbonate, dicetyl peroxydicarbonate,bis(4-tert-butylcyclohexyl) peroxydicarbonate, dicyclohexylperoxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, andhydroperoxides, such as tert-butyl hydroperoxide, and cumenehydroperoxide, alone or intermixed. In aqueous emulsion polymerization,conventional initiators, such as sodium, potassium, and ammoniumperoxodisulfates or alternatively redox systems known to the personskilled in the art can be used.

[0085] The manner in which the initiator is added to the polymerizationvessel during the free-radical polymerization, is known to the personpossessing average skill in the art. It may be placed in thepolymerization vessel as a single initial batch, or it may be usedcontinuously or stepwise at the rate at which it is consumed during thefree-radical polymerization. Specifically, this depends on the chemicalnature of the initiator system and on the polymerization temperature.Preferably, a small portion is used as initial batch and the rest is fedto the polymerization zone at the rate at which it is consumed. It isfrequently advantageously when the polymerization reaction is controlledsuch that first of all ≦50 wt %, often ≦45 wt %, or ≦40 wt % of theinitiator is fed to the polymerization vessel continuously over arelatively long period of time and then >50 wt %, often ≧55 wt %, or ≧60wt % of the initiator is fed in continuously over a shorter period oftime.

[0086] Polymerization can be carried out in conventional manner inpolymerization apparatus, generally equipped with an agitator, severalfeed boxes or feed pipes, a reflux condenser and heating and coolingmeans and designed for operation under an atmosphere of inert gas underpressures above or below atmospheric pressure.

[0087] Following polymerization in solution, the solvents can beseparated, optionally under reduced pressure, this being done at anelevated temperature of up to 150° C. The novel copolymers can then beused in a low-solvent or solventless state, ie as a melt, as adhesives,preferably self-adhesives and, in particular, hot-melt adhesives, or asUV-curable binding agents in coating compositions, such as protectivematerials for coating mineral surfaces or as paints. It may in manycases be advantageous to prepare the novel copolymers bycopolymerization in substance, ie without the assistance of a solvent,in which case production may take place batchwise or continuously, forexample, as described in U.S. Pat. No. 4,042,768.

[0088] If the novel copolymers are used in the form of solutions, forexample, as UV-curable binding agents in coating compositions, such asprotective materials for coating mineral surfaces or as paints, thecopolymer solutions usually contain from 1 to 900 parts by weight,preferably from 10 to 100 parts by weight, and more preferably from 20to 40 parts by weight of solvent per 100 parts by weight of copolymer.Frequently, the copolymer solutions obtained by solvent polymerizationcan be used unchanged for these purposes, or they can be producedtherefrom by simple dilution or concentration.

[0089] In some cases, for example, when the novel copolymers areproduced by aqueous free-radical emulsion polymerization, it is possibleto include conventional regulators in conventional amounts, for example,in concentrations of from 0.1 to 10 parts by weight or from 0.5 to 5parts by weight per 100 parts by weight of the monomers to bepolymerized. Such regulators are used for the regulation of themolecular weight of the copolymers and are known to the person skilledin the art. Frequently, use is made of mercapto compounds, such as2-mercaptoethanol, methyl 3-mercaptopropionate,3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane,3-mercaptopropionic acid, n- or tert-dodecyl mercaptan,1,6-dimercaptohexane, 1,9-dimercaptononane, hydrocarbons, such ascumene, alcohols, such as isopropanol and isobutanol or halogenatedhydrocarbons, such as carbon tetrachloride, carbon tetrabromide,chloroform, or bromoform, ethers, such as tetrahydrofuran and dioxan, asregulators.

[0090] If the novel copolymers are produced by aqueous free-radicalemulsion polymerization, polymerization is usually carried out in thepresence of dispersing agents. The dispersing agents used can beprotective colloids and/or emulsifiers as are familiar to the personskilled in the art, for example, non-ionic and anionic or cationicemulsifiers. Preferably, non-ionic and anionic emulsifiers are used. Theconcentration of dispersant is usually up to 30 parts by weight,preferably from 0.5 to 10 parts by weight, and more preferably from 1 to6 parts by weight, based on 100 parts by weight of the monomers to bepolymerized.

[0091] Frequently, unconverted monomers are removed from the reactionmixture on completion of copolymerization. In the case of solventpolymerization, this is carried out at the same time as the removal ofsolvent under reduced pressure. In order to increase the efficiency,particularly on an industrial scale, the copolymer is stripped withsteam when the solvent has been removed. This steam stripping islikewise frequently carried out on completion of free-radical emulsionpolymerization, optionally after an interposed post-polymerization step,such as is known to the person skilled in the art, for example, fromspecifications WO 95/33775, EP-A 767,180, or DE-A 19743759. It issignificant that the photoinitiators of the invention, in copolymerizedor non-copolymerized form, show better resistance to hydrolysis by wateror other protic organic solvents, such as isopropanol or isobutanol,than the copolymerizable photoinitiators of the prior art.

[0092] When use is made of the novel copolymers, they can be modified inconventional manner and/or subjected to ancillary processing and, forexample, used as hot-melt adhesives. Thus there can be added, forexample, conventional tackifying resins, for example, hydrocarbonresins, modified natural colophoniums or chemically modifiedcolophoniums, predominantly consisting of abietic acid or abietic acidderivatives, coumaron-indene resins, terpenephenolic resins, aldehyderesins, or homopolymers, such as poly-2-ethylhexyl acrylate orpoly-α-methylstyrene, further plasticizers, for example, those based onmono-, di- or poly-ester compounds, perchlorinated hydrocarbons orparaffin oils, dyes, and pigments or stabilizing agents orrubber-elastic materials, such as natural or synthetic rubbers,polyvinyl ethers, and also polybutadiene oils, in amounts of from 0.1 to50 wt %, based on the total weight.

[0093] Also suitable for modification are mono- or poly-olefinicallyunsaturated polymolecular compounds, such as polyesterols andpolyetherols esterified with acrylic acid, such as the acrylates oftripropylene glycol, tetraethylene glycol, or other polyethyleneglycols. Likewise suitable are diacrylates and dimethacrylates ofpolytetrahydrofuran having molecular weights of, in most cases, from 250to 2000 (πumber average). Such diolefinically or polyolefinicallyunsaturated compounds may be advantageously used in concentrations offrom 0.1 to 10 parts by weight per 100 parts by weight of copolymer, anddiolefinically unsaturated compounds of this kind having a molecularweight of at least 500 (πumber average) are of particular interest.

[0094] The novel copolymers are particularly suitable for use as meltsor solutions or in the form of aqueous dispersions for the production ofcoatings, protective films and impregnations, and particularlypressure-sensitive adhesives, self-adhesive films, self-adhesive labels,and embossed films. The compositions can be applied in conventionalmanner by brush coating, spraying, rolling, knife coating or pouring,optionally at elevated temperature—mostly in the temperature range offrom 20° to 150° C.—on conventional substrates, for example, paper,paperboard, wood, metals, such as aluminum, plastics films, such asflexible PVC, polyethylene, polyamides, polyethylene glycolterephthalate, and polypropylene.

[0095] If solvents are used, they can be readily evaporated off from thecoatings, optionally at room temperature or slightly elevatedtemperatures, generally at temperatures of from 20° to 150° C. andpreferably at from 50° to 80° C., for which purpose radiant heaters orhot-air rotary blowers are usually used. The possibly dried or predriedcoatings can then be UV-crosslinked by irradiation to give highlyadhesive coatings exhibiting high cohesion combined with good adhesionand excellent resistance to ageing. Irradiation with UV light normallyrequires no inert gas conditions and can usually take place in air. TheUV radiators used can be conventional radiators, for example, low-,medium-, and high-pressure mercury arc lamps having a power output offrom 20 to 100 J/sec×cm². Lamps of higher power output generally causefaster crosslinking. In some cases, the crosslinking irradiation may beaccompanied, due to the infra-red emission of the lamps, by the removalof residual solvent or water.

[0096] The adhesive properties of flat substrates exhibiting aself-adhesive layer can be determined by measuring the shear strength asa measure of cohesion and the peel strength as a measure of surfacetack.

EXAMPLES

[0097] I Production of Copolymerizable Photoinitiators

[0098] I a) Ethylene glycol p-benzophenone ether

[0099] In a laboratory autoclave having a capacity of 2 L there wereplaced 520 g of diethylene glycol diethyl ether, 286 g ofp-hydroxybenzophenone (>98 wt %), and 0.8 g of powdered potassiumhydroxide. A pressure test was then carried out for 30 minutes using drynitrogen. Following pressure let-down to atmospheric pressure andheating of the reaction mixture under a blanket of nitrogen to 120° C.,95.4 g of ethylene oxide were continuously forced in to give a maximuminternal pressure of 4 bar over a period of 1 h. On completion ofgassing with ethylene oxide, the reaction mixture was allowed to react,until the pressure remained constant for at least 30 minutes. Thereaction mixture was discharged from the autoclave in the hot state,neutralized with 5 wt % strength aqueous hydrochloric acid, and pouredinto 2 L of ice water, and the reaction product was caused tocrystallize by constant agitation. The resulting solid matter wasfiltered off in vacuo, washed with ice water and dried in vacuo (40° C.,10 mbar absolute). The resulting filtrate was concentrated in a rotaryfilm evaporator to 20% of its volume, the precipitated product filteredoff in vacuo, washed with ice water and likewise dried in vacuo. Thetotal yield was 82% of theory.

[0100] I b) Copolymerizable Photoinitiators, General ProductionInstructions

[0101] 1 mol of isocyanate as given in Table 1 was dissolved inanhydrous tetrahydrofuran (THF) at from 20° to 25° C. (ambienttemperature) such that the urethane adduct produced in the firstreaction step subsequently existed as a 35 wt % strength solution. Aftercovering with dry nitrogen, 1 mol of hydroxyethyl acrylate, previouslystabilized with 100 ppm of Tempol, was then added within a period of 5minutes at room temperature. 500 ppm by weight (based on isocyanateused) of dibutyltin dilaurate were then added, and the mixture wasstirred for approximately 5 hours at 50° C. while the fall in isocyanatecontent was monitored titrimetrically. Once the theoretical isocyanatecontent of the monourethane had been achieved, the molar amount ofethylene glycol p-benzophenone ether groups corresponding to theisocyanate still free is added as a 35 wt % strength solution from stageIa) in THF having a temperature of 50° C. The reaction mixture was thenfurther stirred at 50° C. until no more isocyanate groups could bedetected titrimetrically. The resulting reaction mixtures were useddirectly in the following polymerization reaction. TABLE 1 Isocyanatesand solvents Photoinitiator Isocyanate A 2,4-toluylene diisocyanate Bisophorone diisocyanate C HDI-polyisocyanate 2,4-Toluylene diisocyanate:95 wt %, Fluka AG isophorone diisocyanate: Vestanat ® IPDI, Degussa-HlsAG HDI-polyisocyanate: Basonat ® HI 100, BASF AG dibutyltin dilaurate:95 wt %, Merck-Schuchardt tetrahydrofuran: 99.9 wt %, anhydrous2-hydroxyethyl acrylate: ≧98.5 wt %, BASF AG Tempol: 2,2,6,6-tetramethylpiperidin-1-oxyl-4-ol, 98 wt %, Aldrich-Chemie

[0102] I c) 4-(4-benzoylphenoxycarbonyloxy)-n-butyl acrylate(comparative photoinitiator)

[0103] The synthesis of 4-(4-benzoylphenoxycarbonyloxy)-n-butyl acrylatewas carried out according to the teaching of EP-A 377,199. In thecomparative example, a 35 wt % strength solution of the comparativephotoinitiator in o-xylene was used.

[0104] II Production of the Copolymers

Example 1

[0105] In a reactor having a capacity of 2 L and provided with heatingand cooling means and equipped with an anchor agitator, reflux condenserand evacuating and metering equipment there were placed, at roomtemperature under a blanket of nitrogen,

[0106] 108.5 g of isobutanol (IB; 99.5 wt %)

[0107] 50.5 g of feed stream 0.1 and

[0108] 4.3 g of feed stream 2

[0109] and the mixture was heated to 100° C. with stirring with theapparatus closed but without pressure compensation. Startingconcurrently, the residual amount of feed stream 1 was metered in atthis temperature over a period of 3 hours and the residual amount offeed stream 2 over a period of 3.5 hours. 15 minutes after completion offeed 2, feed 3 was commenced, this being metered in over a period of 15minutes. At the same time as feed stream 3 was metered, the temperaturewas raised to 120° C.

[0110] On conclusion of feed 3, polymerization was continued for afurther hour at 120° C. The temperature was then lowered to 100° C. andthe pressure gently let down to atmospheric pressure, after which thesolvent and the other low-boiling components were removed bydistillation by careful application of vacuum to a final pressure of 10mbar (absolute). The reaction batch was then cooled to room temperature.

[0111] Feed Stream 1

[0112] 491.0 g of n-butyl acrylate (π-BA; >99.5 wt %, BASF AG)

[0113] 278.5 g of 2-ethylhexyl acrylate (EHA; >99.6 wt %, BASF AG)

[0114] 189.0 g of methyl methacrylate (MMA; >99.9 wt %, BASF AG)

[0115] 23.0 g of acrylic acid (AA; >99.0 wt %, BASF AG)

[0116] 15.1 g of a 35 wt % strength solution of photoinitiator A in THF

[0117] Feed Stream 2

[0118] 41.7 g of IB

[0119] 0.3 g tert.-Butylper-2-ethylhexanoat (TBEH; >

[0120] 98.5 wt %, sold by Peroxid-Chemie GmbH)

[0121] Feed Stream 3

[0122] 16.7 g of IB

[0123] 2.0 g of TBEH

[0124] There was obtained a clear, highly viscous polymer having asolids content of >99,9 wt %.

[0125] The solids content was generally determined by heating from 1 to2 g of the resulting polymer at 140° C. to constant weight in analuminum crucible having a diameter of ca 3 cm, under atmosphericpressure. In each case two readings were taken. The values givenrepresent the averages of these readings. In all of the followingexamples solids contents of >99,9 wt % were likewise found.

[0126] The K value of the copolymer was 50.5.

[0127] The K values of the copolymers were generally determined asspecified by H. Fikentscher, Cellulosechemie 1932 (13) pages 58 to 64and pages 71 to 74, where K is equal to k×103. The readings were takenat 25° C. on a 1 wt % strength solution of the copolymers in THF(corresponding to DIN ISO 1628-1).

Comparative Example

[0128] The comparative example was carried out in a manner similar tothat described in Example 1 with the exception that instead of thephotoinitiator A the same amount of the comparative photoinitiator wasused. The K value was found to be 50.5.

Example 2

[0129] Example 2 was carried out in a manner similar to that describedin Example 1 exception that instead of IB use was made of methyl ethylketone (MEK; ≧99.0 wt %, Deutsche Shell Chemie GmbH). A K value of 51.8was found.

Example 3

[0130] Example 3 was a repetition of Example 1 except that instead ofthe photoinitiator A the identical amount of photoinitiator B was used.The K value was found to be 48.0.

Example 4

[0131] Example 4 was a repetition of Example 1 except that instead ofthe photoinitiator A the identical amount of photoinitiator C was used.The K value was found to be 48.6.

Example 5

[0132] Example 5 was a repetition of Example 1 except that 30.2 g of a35 wt % strength solution of photoinitiator A in THF were used. The Kvalue was found to be 52.0.

Example 6

[0133] Example 6 was a repetition of Example 1 except that in the feedstreams 2 and 3 instead of TBEH 2,2′-azobis-2-methylbutyronitrile (WakoV59, WAKO Chemicals GmbH) were used. The K value was found to be 49.6.

Example 7

[0134] In a reactor having a capacity of 2 L and provided with heatingand cooling means and equipped with an anchor agitator, reflux condenserand evacuating and metering equipment

[0135] 110.5 g of IB

[0136] 52.5 g of feed stream 1 and

[0137] 4.0 g of feed stream 2

[0138] were used as initial batch at room temperature under a blanket ofnitrogen and heated to 100° C. in closed apparatus without pressurecompensation, with stirring. Starting concurrently, the residual amountof feed stream 1 was metered in at this temperature over a period of 3hours and the residual amount of feed stream 2 over a period of 3.5hours. 15 minutes after completion of feed 2, feed 3 was commenced, thisbeing metered in over a period of 15 minutes. At the same time as feedstream 3 was metered, the temperature was raised to 120° C.

[0139] On conclusion of feed 3, polymerization was continued for afurther hour at 120° C. The temperature was then lowered to 100° C. andthe pressure carefully let down to atmospheric pressure, after which thesolvent and other low-boiling components were removed by distillation bygentle application of vacuum to a final pressure of 10 mbar (absolute).The batch was then cooled to room temperature. There was obtained aclear, highly viscous polymer having a solids content of >99,9 wt %. TheK value was found to be 50.5.

[0140] Feed Stream 1

[0141] 422.0 g of n-BA

[0142] 347.5 g of EHA

[0143] 189.0 g of MMA

[0144] 25.0 g of AA

[0145] 12.3 g of a 35 wt % strength solution of photoinitiator A in THF

[0146] Feed Stream 2

[0147] 41.7 g of IB

[0148] 0.4 g of TBEH

[0149] Feed Stream 3

[0150] 16.7 g of IB

[0151] 2.4 g of TBEH

Example 8

[0152] Example 8 was carried out in a manner similar to that describedin Example 7 except that instead of IB there was used MEK. A K value of48.8 was found.

Example 9

[0153] Example 9 was a repetition of Example 7 except that instead ofthe photoinitiator A the identical amount of photoinitiator B was used.The K value was found to be 48.6.

Example 10

[0154] Example 10 was a repetition of Example 7 except that instead ofthe photoinitiator A the identical amount of photoinitiator C was used.The K value was found to be 48.6.

Example 11

[0155] Example 5 was a repetition of Example 7 except that 24.6 g of a35 wt % strength solution of photoinitiator A in THF were used. The Kvalue was found to be 50.2.

Example 12

[0156] Example 12 was a repetition of Example 7 except that in the feedstreams 2 and 3 instead of TBEH Wako V59 was used. The K value was foundto be 48.5.

Example 13

[0157] In a reactor having a capacity of 2 L and provided with heatingand cooling means and equipped with an anchor agitator, reflux condenserand evacuating and metering equipment

[0158] 115.0 g of IB

[0159] 59.5 g of feed stream 1 and

[0160] 3.3 g of feed stream 2

[0161] were used as initial batch at room temperature under a blanket ofnitrogen and heated to 100° C. in closed apparatus without pressurecompensation, with stirring. Starting concurrently, the residual amountof feed stream 1 was metered in at this temperature over a period of 3.5hours and the residual amount of feed stream 2 over a period of 4 hours.15 minutes after completion of feed 2, feed 3 was commenced, this beingmetered in over a period of 15 minutes. At the same time as feed stream3 was metered, the temperature was raised to 115° C.

[0162] On conclusion of feed 3, polymerization was continued for anothertwo hours at 115° C. The temperature was then lowered to 100° C. and thepressure carefully let down to atmospheric pressure, after which thesolvent and other low-boiling components were removed by distillation bygentle application of vacuum to a final pressure of 10 mbar (absolute).The batch was then cooled to room temperature. There was obtained aclear, highly viscous polymer having a solids content of >99,9 wt %. TheK value was found to be 50.1.

[0163] Feed Stream 1

[0164] 1117.0 g of n-BA

[0165] 59.1 g of AA

[0166] 11.5 g of a 35 wt % strength solution of photoinitiator A in THF

[0167] Feed Stream 2

[0168] 65.8 g of IB

[0169] 1.3 g of TBEH

[0170] Feed Stream 3

[0171] 19.7 g of IB

[0172] 2.6 g of TBEH

Example 14

[0173] In a reactor having a capacity of 2 L and provided with heatingand cooling means and equipped with an anchor agitator, reflux condenserand evacuating and metering equipment

[0174] 115.0 g of IB

[0175] 59.5 g of feed stream 1 and

[0176] 3.3 g of feed stream 2

[0177] were used as initial batch at room temperature under a blanket ofnitrogen and heated to 100° C. in closed apparatus without pressurecompensation, with stirring. Starting concurrently, the residual amountof feed stream 1 was metered in at this temperature over a period of 3.5hours and.the residual amount of feed stream 2 over a period of 4 hours.15 minutes after completion of feed 2, feed 3 was commenced, this beingmetered in over a period of 15 minutes. At the same time as feed stream3 was metered, the temperature was raised to 115° C.

[0178] On conclusion of feed 3, polymerization was continued for anothertwo hours at 115° C. The temperature was then lowered to 100° C. and thepressure carefully let down to atmospheric pressure, after which thesolvent and other low-boiling components were removed by distillation bygentle application of vacuum to a final pressure of 10 mbar (absolute).The batch was then cooled to room temperature. There was obtained aclear, highly viscous polymer aving a solids content of >99,9 wt %. TheK value was found to be 50.5.

[0179] Feed Stream 1

[0180] 1100.0 g of n-BA

[0181] 55.1 g of AA

[0182] 22.0 g of maleic anhydride (MA; >99,7 wt %, Lonza S.P.A.)

[0183] 11.5 g of a 35 wt % strength solution of photoinitiator A in THF

[0184] Feed Stream 2

[0185] 65.8 g of IB

[0186] 1.3 g of TBEH

[0187] Feed Stream 3

[0188] 19.7 g of IB

[0189] 2.6 g of TBEH

Example 15

[0190] In a reactor having a capacity of 2 L and provided with heatingand cooling means and equipped with an anchor agitator, reflux condenserand evacuating and metering equipment

[0191] 115.0 g of IB

[0192] 59.5 g of feed stream 1 and

[0193] 3.3 g of feed stream 2

[0194] were used as initial batch at room temperature under a blanket ofnitrogen and heated to 100° C. in closed apparatus without pressurecompensation, with stirring. Starting concurrently, the residual amountof feed stream 1 was metered in at this temperature over a period of 3.5hours and the residual amount of feed stream 2 over a period of 4 hours.15 minutes after completion of feed 2, feed 3 was commenced, this beingmetered in over a period of 15 minutes. At the same time as feed stream3 was metered, the temperature was raised to 115° C.

[0195] On conclusion of feed 3, polymerization was continued for anothertwo hours at 115° C. The temperature was then lowered to 100° C. and thepressure carefully let down to atmospheric pressure, after which thesolvent and other low-boiling components were removed by distillation bygentle application of vacuum to a final pressure of 10 mbar (absolute).The batch was then cooled to room temperature. There was obtained aclear, highly viscous polymer having a solids content of >99,9 wt %. TheK value was found to be 49.3.

[0196] Feed Stream 1

[0197] 1043.0 g of n-BA

[0198] 133.1 g of AA

[0199] 22.0 g of a 35 wt % strength solution of photoinitiator A in THF

[0200] Feed Stream 2

[0201] 65.0 g of IB

[0202] 1.7 g of TBEH

[0203] Feed Stream 3

[0204] 19.9 g of IB

[0205] 2.6 g of TBEH

Example 16

[0206] Example 16 was carried out in a manner similar to that describedin Example 15 except that the following feed streams were used:

[0207] Feed Stream 1

[0208] 1000.0 g of n-BA

[0209] 105.1 g of AA

[0210] 72.0 g of MA

[0211] 13.5 g of a 35 wt % strength solution of photoinitiator A in THF

[0212] Feed Stream 2

[0213] 68.4 g of IB

[0214] 1.7 g of TBEH

[0215] Feed Stream 3

[0216] 19.7 g of IB

[0217] 2.8 g of TBEH

[0218] The K value was found to be 48.6.

Example 17

[0219] In a reactor having a capacity of 2 L and provided with heatingand cooling means and equipped with an anchor agitator, reflux condenserand evacuating and metering equipment

[0220] 110.0 g of IB

[0221] 59.0 g of feed stream 1 and

[0222] 2.5 g of feed stream 2

[0223] were used as initial batch at room temperature under a blanket ofnitrogen and heated to 100° C. in closed apparatus without pressurecompensation, with stirring. Starting concurrently, the residual amountof feed stream 1 was metered in at this temperature over a period of 4hours and the residual amount of feed stream 2 over a period of 4.5hours. 15 minutes after completion of feed 2, feed 3 was commenced, thisbeing metered in over a period of 15 minutes. At the same time as feedstream 3 was metered, the temperature was raised to 115° C.

[0224] On conclusion of feed 3, polymerization was continued for anothertwo hours at 115° C. The temperature was then lowered to 100° C. and thepressure carefully let down to atmospheric pressure, after which thesolvent and other low-boiling components were removed by distillation bygentle application of vacuum to a final pressure of 10 mbar (absolute).The batch was then cooled to room temperature. There was obtained aclear, highly viscous polymer having a solids content of >99,9 wt %. TheK value was found to be 46.5.

[0225] Feed Stream 1

[0226] 910.0 g of EHA

[0227] 91.0 g of hydroxyethyl acrylate (>98,5 Gew.-%, BASF AG)

[0228] 22.2 g of a 35 wt % strength solution of photoinitiator A in THF

[0229] Feed Stream 2

[0230] 35.8 g of IB

[0231] 0.8 g of TBEH

[0232] Feed Stream 3

[0233] 21.7 g of IB

[0234] 2.8 g of TBEH

[0235] The K value was found to be 48.6.

[0236] III Utilitarian Tests

[0237] The copolymers produced in Examples from 1 to 17 were subjectedto utilitarian tests to examine their self-adhesive properties. Theprocedure was as follows:

[0238] a) Production of Test Strips

[0239] The copolymer to be tested was examined without the addition oftackifiers. For this purpose the copolymer was thinly applied to acommercial polyester film (Hostaphan RN 36 film) on a heated spreadingbench at from 85° to 120° C. with a doctor blade and then cooled to roomtemperature. The radial screw clearance of the doctor blade was set togive a rate of copolymer application of from 19 to 21 g/m². Irradiationwas effected with a CK radiator, sold by IST-Strahlentechnik Metz GmbHand having a power output of 75 mJ/sec×cm². For this purpose the coatedfilm was laid on a travelling continuous web so that the coated filmpassed under the lamp at a distance of 10 cm and at a rate of 58 m/min.Irradiation took place in air. The films thus produced were cut up intotapes 2.5 cm wide and 25 cm long.

[0240] b) Test of Shear Strength (Similar to FINAT FTM 7)

[0241] Each strip was stuck to the marginal region of a test plate ofhigh-grade steel such that a stick-on area of 12.5×12.5 mm2 wasobtained. 10 minutes after the strip had been stuck to the plate a 1000g weight was fixed to the loose end of the strip and the test plate washung vertically in a chamber having a constant temperature of 23° C. anda relative humidity of 50%. The time taken for the weighted tape to tearaway from the plate is a measure of the shear strength, which is in turna measure of cohesion. The more time required to break the adhesivebond, the greater the cohesion. Three separate tests were carried out oneach polymer. The values given in Table 2 are averages of the results ofsaid tests.

[0242] c) Test of the Peel Strength (Similar to FINAT FTM 1)

[0243] A test strip was stuck to a stainless steel test plate at 23° C.and 50% relative humidity.

[0244] Following a specified contact time of 24 hours, the tape waspulled off the plate with a tension tester at an angle of 180° and at arate of 300 mm per minute. The required force is a measure of theadhesion. It is termed peel strength and is expressed in terms of newtonper 2.5 cm (N/2.5 cm). The degree of adhesion is higher, the higher thevalue of the peel strength after the stated time. Three separate testswere carried out on-each polymer. The values given in Table 2 areaverages of the results of said tests. TABLE 2 Summary of the shearstrengths and peel strengths of the copolymers of Examples from 1 to 17Peel strength in Shear strength in N/2.5 cm after 24 Polymer of Exampleminutes hours  1 135 10.2 Comparison 75 9.7  2 125 12.7  3 110 17.1  490 17.0  5 148 10.5  6 111 12.0  7 115 12.9  8 105 12.1  9 108 14.3 10101 14.0 11 137 10.9 12 106 11.1 13 130 10.5 14 115 10.8 15 111 12.1 16108 10.9 17 118 11.8

[0245] As is clearly visibly from Table 2, the hot-melt adhesives of theinvention exhibit distinctly higher shear strengths (cohesion) than aself-adhesive during the production of which a photoinitiator is usedwhich is not of the invention. Greatly improved are also the peelstrengths (adhesion) as measured after a period of 24 hours.

1. A process for the production of a UV-crosslinkable copolymer, whichcomprises free-radically polymerizing a mixture of ethylenicallyunsaturated monomers comprising a free-radically copolymerizableacetophenone or benzophenone derivative obtained by reaction of a) a(meth)acrylic compound exhibiting at least one isocyanate-reactivegroups compound a), with b) a compound having at least two isocyanategroups compound b), and c) an acetophenone or benzophenone derivativeexhibiting at least one isocyanate-reactive group, compound c).
 2. Aprocess as defined in claim 1, wherein the compound a) is a(meth)acrylic compound of formula (I) H₂C═CR¹—C(═O)—X—R²(—Y)_(π)  (I),in which the substituents and indices have the following meanings: R¹denotes —H, —CH₃, X denotes —O—, —NH—, —NR³— or —S—, R³ denotes linearor branched C₁-C₆ alkyl, R² denotes a (π+1)-binding, optionallysubstituted linear or branched C₁-C₁₂ alkyl group, or a C₃-C₁₂cycloalkyl group, optionally substituted, or a C₆-C₁₀ aryl group,optionally substituted, Y denotes —OH, —NH2, —NHR³, or —SH, π is anumber from 1 to 5, while the structural element —R²(—Y), in formula (I)can alternatively be a group of formula (II), (III), or (IV)—(EO)_(k)—(PO)_(l)—H  (II), —(PO)_(l)—(EO)_(k)—H  (II),—(Eo_(k)/PO_(l))—H  (IV), in which EO stands for a —CH₂—CH₂—O group, POstands for a —CH₂—CH(CH₃)—O or a —CH(CH₃)—CH₂—O group and k and 1 arenumerical values of from 0 to 15, but k and 1 are not both
 0. 3. Aprocess as defined in claim 1, wherein compound b) is a compound offormula (V) Q(—NCO)_(λ)  (V), in which Q is a linear or branched C₃-C₁₆alkane compound, optionally substituted by 1, 2, or 3 halogens, oxo,ester, or alkoxy groups, or a C₆-C₁₄ aromatic compound, optionallysubstituted by 1, 2, or 3 halogens, or C₁-C₆ alkyl, oxo, ester, oralkoxy groups, or a C₃-C₁₆ cycloalkane compound, optionally substitutedby 1, 2, or 3 halogens, C₁-C₆ alkyl, oxo, ester, or alkoxy groups, or anarylalkyl compound containing from 6 to 10 carbons in the aryl moietyand from 1 to 6 carbon atoms in the alkyl moiety, optionally substitutedby 1, 2, or 3 halogens, oxo, ester, or alkoxy groups, and λ is a number≧2.
 4. A process as defined in claim 1, wherein compound c) is anacetophenone or benzophenone derivative of formula (VI)A-C(═O)-B-D  (VI), in which the substituents have the following meaning:A denotes C₁-C₃ alkyl, C₆-C₁₀ aryl, optionally substituted by 1, 2, or 3halogens, C₁-C₆ alkyl, ester, or alkoxy groups, and aralkyl containingfrom 6 to 10 carbons in the aryl moiety and from 1 to 6 carbons in thealkyl moiety, B denotes C₆-C₁₀ arylene, optionally substituted by 1, 2,or 3 halogens, C₁-C₆ alkyl, ester, or alkoxy groups and D denotes —NH2,—NHR3, OH, SH, or a structural element —X—R²(—Y), the variants havingthe meanings stated for formula (I).
 5. A process as defined in claim 2,wherein, in compound a), Y denotes —OH and π denotes 1, in compound b),λ denotes 2, and, in compound c), A denotes methyl or phenyl, B denotes1,4-phenylene, and D denotes —O—CH₂CH₂—OH.
 6. A process as defined inclaim 2, wherein the ratio of the number of mols of compound b) to theproduct of the number of mols of compound a) and the number π is from0.8:1 to 1:0.8.
 7. A copolymer obtainable by a process as defined inclaim
 1. 8. A copolymer as defined in claim 7 having a glass transitiontemperature of from −70 to +150° C.
 9. The use of a copolymer as definedin claim 7 as a UV-curable binding agent or adhesive.
 10. The use of acopolymer as defined in claim 7 as a pressure-sensitive adhesive,particularly a hot-melt pressure-sensitive adhesive.
 11. A UV-curablebinding agent or adhesive, which comprises the copolymer as claimed inclaim
 7. 12. A UV-curable binding agent or adhesive, which comprises thecopolymer as claimed in claim
 8. 13. A pressure-sensitive adhesive,which comprises the copolymer as claimed in claim
 7. 14. A hot-meltpressure-sensitive adhesive, which comprises the copolymer as claimed inclaim
 7. 15. A pressure-sensitive adhesive, which comprises thecopolymer as claimed in claim
 8. 16. A hot-melt pressure-sensitiveadhesive, which comprises the copolymer as claimed in claim 8.